Recently, the demand for magnetic field sensors for electronic compass applications has been increasing rapidly as GPS functionality in hand-held devices, for example, cellular phones, personal navigation devices, etc., includes such functions. Recent studies have shown that, even with the current slowing global economy, GPS-enabled handsets sales are expected to reach over 240 million units in 2009. This will be an increase of over 6% from 2008 while the overall cellular phone market is expected to shrink by 4% to 8%. Magnetic sensors enhance GPS mobile phones in many aspects, including dead reckoning, map orientation, initial heading indication, and especially, location-based services.
Magnetic field sensors based on anisotropic magnetoresistive (AMR) technology are well known. Examples of such technology are described in U.S. Pat. Nos. 4,847,584; 5,247,278; 5,521,501 and 5,952,825, each of which is herein incorporated by reference for all purposes.
What is needed however, is an accurate magnetic field sensor that is small in size, low cost, that requires low power as is necessitated by mobile device applications, is easy to use and that is easily incorporated into a mobile device.